Optional dependencies: osgEarth will compile without them. Look and decide what you need

GEOS 3.2.0 or later - C++ library for topological operations.
osgEarth uses GEOS to perform various geometry operations like buffering and intersections.
If you plan to use vector feature data in osgEarth, you probably want this.

QT_ 5.4 or later - Cross-platform UI framework. Used to built the osgEarthQt support library, which is
useful (though not required) for building Qt applications that us osgEarth. Point the
QT_QMAKE_EXECUTABLE CMake variable to the qmake.exe you want to use and CMake will
populate all the other QT variables.